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The Enduring Legacy of Kant's Critique of Pure Reason
Critique of Pure Reason - Book Overview and Thoughts
“…In respect of time, therefore, no knowledge of ours is antecedent to experience, but begins with it. But, though all our knowledge begins with experience, it by no means follows that all arises out of experience” - Immanuel Kant
Have you ever stopped to wonder about the limits of human knowledge? How much can we really know about the world around us, and what are the boundaries of our understanding?
These are the questions that Immanuel Kant set out to answer in a revolutionary way.
Kant’s Critique of Pure Reason is a wild ride through the mysteries of the human mind, a quest to uncover the secrets of how we know what we know.
Kant dives deep into questions such as: is there anything we can know for sure, without needing to rely on our senses? Can we have objective knowledge? And what are the limits of reason when it comes to understanding the world?
Overall, “The Critique of Pure Reason” can be understood as a critique conducted by reason critiquing its own self.
So, who was Kant?
Immanuel Kant was a student of Christian Wolf, who was a student of Leibniz, a rationalist. Kant, therefore, saw himself as a part of the rationalist tradition. However, once he read David Hume, an empiricist, he realized that something was missing, and tried to reconcile the claims of these two theories.
Rationalists established reason as the sole criteria for truth, originating from René Descartes, who was influenced by his time and attempted to demonstrate that truth cannot be based on theological and superstitious beliefs. The theory seeks to prove that the natural world can be understood and explained by the use of reason alone, and that knowledge obtained this way is more reliable and trustworthy than the one obtained through only sensory experience.
Mathematics, for instance, is a method of obtaining the principles that govern our world, because these are already there in reason before any experience is applied to them.
On the other hand, David Hume’s empiricism saw all of this with skepticism. His theory rejected a lot of what the rationalists claimed, and argued that senses and experiences are the only ways to gain knowledge of reality. For empiricists, there is nothing in the background that tells you how to perceive the world; instead, humans only perceive things that appear to be frequently the same, giving us a feeling that that event will happen again.
In other words, empiricists recognized that there are universals about how we experience the world, such as cause and effect, but that they do not come from reason. They are instead generated exclusively from the senses.
Before we get into the details of the book, here are some highlights:
Kant talks about the concepts of analytic and synthetic judgments, and a priori and a posteriori knowledge.
Analytic judgments are statements that are true by definition, while synthetic judgments require empirical evidence to be verified.
A priori knowledge is independent of experience and can be known through reason alone, while posteriori knowledge is dependent on experience and can only be known through observation.
Kant claimed that we can have judgments that are a priori and synthetic at the same time, which means that they do not repeat the meaning of a concept themselves, but add new knowledge that is not contained within them.
Kant distinguished between phenomena and noumena, where phenomena are the objects of our experience, and noumena are the “things in themselves,” or the objects as they exist independently of our experience.
Kant’s theory of Transcendental Idealism suggests that our minds play an active role in shaping the world we experience, and that human knowledge is made possible by the combination of our senses and our reasoning faculties.
Space and time are a priori forms of sensibility since they are the ones receiving through perception, and so they are pure intuition. Using our senses, we can determine where something is and how objects change over time.
Kant introduced the idea of categories of the understanding, which are basic concepts that our minds actively use to structure information and make it intelligible.
Kant’s Transcendental Deduction describes how our minds actively synthesize information and impose specific structures, like categories or concepts, on the unprocessed sensory data to make sense of it. It is through this process of information that we are able to develop accurate perceptions and judgments of the world around us.
Now, let’s dive deep into it!
Understanding Kant's Main Concepts
After explaining what Kant was into, we can dive into the concepts he talks about in his book.
We can now answer questions like: How do we make sense of all the chaos that comes from experience? How can we give meaning to each little piece out of a great chaos of information?
The main concepts he talks about are the distinction between analytic and synthetic judgments, and a priori and a posteriori knowledge.
Analytic judgments are statements that are true by definition. For instance, the statement “All squares have four sides” is an analytic judgment because the concept of “four sides” is already contained in the concept of a square. We do not need to say that a square has four sides to prove it has four sides.
In fact, Kant used one particular example in his book, which was, “All bachelors are unmarried.”
In this case, the definition of “unmarried” is already contained in the concept of “bachelor.”
This means that, if you understand the meaning of the words “square” and “bachelor,” you will automatically understand that squares have four sides and that bachelors are unmarried, respectively. Without the need of new information.
In contrast, synthetic judgments are statements that are not true by definition, and require empirical evidence to be verified.
For example, “The cat is sitting on the mat” is a statement that requires empirical evidence to be verified. We can only know that the cat is sitting on the mat by observing the cat and the mat, and not just by observing the cat or the mat independently.
This brings us to Kant’s claim about the different sorts of knowledge. The first is a priori knowledge, which is independent of experience and can be obtained through reason alone.
An example of this is a mathematical truth, such as “2+2=4.” For this, you do not need to observe the world to know that the statement is true. You can simply reason it out using your understanding of math.
On the contrary, posteriori knowledge is dependent on experience and can only be known through observation.
An example could be the statement “The sky is blue.” In this case, we need to see the sky to know that it is blue, and we cannot know the truth of the statement without observation.
Now, you may ask, why do these distinctions matter?
Well, for Kant, a priori knowledge is special because it allows us to have universal and necessary knowledge. In other words, it gives us access to truths that are true for everyone, everywhere, and at all times. And this, in turn, is the foundation for all of our other knowledge.
On the other hand, synthetic judgments are important because they allow us to learn new things about the world. They're what gives us new information that we didn't already know, and increase our understanding of the world.
If we connect the dots, we can understand that analytic judgments are a priori knowledge, and synthetic judgments are posteriori knowledge.
However, Kant claimed that we can have judgments that are a priori and synthetic at the same time.
This means that we can have judgments that do not repeat the meaning of a concept themselves, and add new knowledge that is not contained within them.
In fact, Kant claimed that much of our knowledge is synthetic. He believed that most of our knowledge combines empirical observation with our innate reasoning faculties, which we will talk about in a second.
Kant's Transcendental Idealism: How our minds shape the world we experience
Kant believed that we do not have access to “things in themselves,” and that all we have access to is to our subjective constructs.
With this in mind, another key aspect of Kant’s theory is his distinction between phenomena and noumena. Phenomena are basically the objects of our experience, and noumena are the “things in themselves,” or in other words, the objects as they exist independently of our experience.
These concepts form the foundation for Kant’s theory of Transcendental Idealism. That claims that our minds actively shape the world we perceive and give structure to the empirical chaos of the outside world. It is the idea that a mental realm exists prior to empirical reality, and that it has a considerable impact on how the world develops into what we know it to be, as well as establishing the framework within which we can understand the world.
In other words, Kant believed that human knowledge was made possible by the combination of our senses and our reasoning faculties. He thought there are principles of reason and sensibility that are independent of the senses, and that these concepts are meaningless unless applied to experience.
This means that all data received through the senses is transformed by reason. Demonstrating that pure experience cannot have meaning or form. To put it another way, our world is a subjective creation, and our reality, our objectivity, is dependent on our senses.
We could think about our minds as projectors, and then our world conforms to them. Our minds are then constituted to process information provided by the senses only in a certain manner. Just like a projector can only interpret information in a certain way.
If we then know our minds, we might be able to know what something is going to look like before it’s even projected. In other words, we can know its appearance. This allows us to understand the a priori of the objects we experience, because we understand how they are being constituted by our minds.
To understand how our minds structure the world, we may start by exploring space and time.
I love talking about the vastness of space and time. But, why did Kant bring these concepts up?
The reason for this is that phenomena must be placed in space and time in order for us to perceive it in the first place. If you think about it, we are unable to comprehend anything outside of these concepts.
Space and time are a priori forms of sensibility since they are the ones receiving through perception, and so they are pure intuition. Using our senses, we can determine where something is and how objects change over time. We may grasp the phenomena and make sense of it in this manner. This is the part of Kant’s Transcendental Idealism known as Transcendental Aesthetic. Which is the first step in making sense of the world's chaos. Aesthetic because it indicates the meaning of “sensibility” in Greek, which literally means “sense perception.”
But then, how can we make sense of the information we receive from space and time? How can we make an interpretation of the data coming from perception?
This is when reasoning faculties come into play.
Kant felt that in order to synthesize all the information from the senses, we needed certain a priori concepts. His transcendental argument is that a priori concepts are necessary for the possibility of experience. That we need some concepts that are already in there in our minds to be able to synthesize information, and to be capable of saying, “this,” “that one,” to have universality, and so on.
We have experience: therefore, it means that there are a priori concepts and categories of the understanding prior to experience.
Understanding is judging, and judging needs concepts. Judgments of logic, concepts that could be related to the objects we perceive.
This is his system’s second idea. He believed that human minds apply basic notions like unity, plurality, totality, reality, negation, limitation, substance, cause-and-effect, reciprocity, possibility, existence, and necessity to synthesize and organize our experiences coming from space and time.
Kant argued that these categories of the understanding are necessary for the human mind to make sense of the world, and that they are not generated from experience, as claimed in his argument. We may learn the words to describe the concepts, but we do not learn the concepts themselves. They are part of the judgments of logic that are built into our minds.
In other words, our minds put certain structures on the world to make sense of it, rather than passively receiving information from it.
For instance, the category of causation allows us to understand that events have causes and effects, while the category of substance enables us to perceive objects as having a consistent identity over time, despite them changing. Additionally, the category of possibility allows us to understand that life may exist on other planets, despite the absence of concrete evidence.
These categories are applied to any possible object we encounter, even if the application is limited to phenomena, rather than the “thing in itself.” This is Kant’s Transcendental Deduction. It is the way we synthesize information, use categories as necessary conditions for experience, and make sense of the chaos that the senses provide us through space and time.
With Kant’s Transcendental Idealism, we can then come to understand that our experiences of the world are not merely the sum of sensory input, but are shaped and mediated by a set of a priori concepts and laws of the understanding; and that these concepts, like the lenses of a camera, allow us to focus our attention and make sense of the world around us in a certain way.
We will never know how the world truly is, but we can embrace and fully learn about it by means of what it seems to be, through our limited human lenses.
We can comprehend the immensity of a landscape or a piece of music by immersing ourselves in it and absorbing every detail while focusing on specific areas of our experience. Synthesizing the information as we perceive it in space and time.
Kant’s philosophy is thus not just about the mechanics of the mind, but it’s also a reminder of the limitations of reason. Kant recognized that our human lenses have limitations, and that we cannot know everything about the universe beyond our experience. Thus, we are limited to knowing our world objectively within the realm of phenomena, and will never have access to how things are in themselves.
This has important implications for the way we approach scientific knowledge, for example. As could be inferred from Kant, science aims to give us a true story about phenomena, but it is limited by the fact that we can only ever observe that phenomena through our human lenses. As a result, for Kant, science can only ever “save the phenomena” - that is, provide us with a description of the way things appear to us - rather than giving us access to things as they are in themselves. This is the opposite of being a scientific realist, who believes that science can provide us with a true story, or in other words, objective knowledge of the world as it really is.
What’s more, Kant’s concept of God is also a complex subject derived from his theory. He concluded that the concept cannot be proven purely by reason, and that it is instead a necessary idea resulting from the limitations of the human mind, like causation, for example. However, he argues that moral law is the result of practical reason, and that this law implies the existence of God as a necessary presupposition. He also maintains that the moral law requires us to see others as ends in themselves, and that the existence of God must exist to ensure this is eventually achieved. In other words, we don’t need religion to make moral laws, but we do need to assume the existence of God, which would be a good topic for another day.
Overall, Kant’s discoveries have profound implications for the study of philosophy, theology, science, and the nature of knowledge itself. Although Kant modified and updated his book several times, the ideas have persisted and continue to influence the way we think about the boundaries of human reason and the nature of our knowledge.
So, can we trust our senses? Can we claim definite objective truth?
Kant’s Critique of Pure Reason is fairly tough, and I have done my best to simplify it. In future posts, we will discuss his ethics and political theory to go deeper into his ideas.
Kant, I. (1787). Critique of Pure Reason (-2nd ed.). Penguin Classics.
(n.d.). Kant’s Transcendental Arguments. Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/kant-transcendental/
(n.d.). Scientific Realism. Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/scientific-realism/
Scruton, R. (2001). Kant: A Very Short Introduction.
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